Scientists have created "artificial embryos" using stem cells from mice, in what they believe is a world first.
The University of Cambridge team used two types of stem cells and a 3D scaffold to create a structure closely resembling a natural mouse embryo.
Previous attempts have had limited success because early embryo development requires the different cells to coordinate with each other.
The researchers hope their work will help improve fertility treatments.
It could also provide useful insights into the way early embryos develop.
However, experimentation on human embryos is strictly regulated, and banned after 14 days.